Signaling system and apparatus



Patented Aug. 11, 1936 UNITED STATES SIGNALING SYSTEM AND APPARATUS Foster E. Weld, Newton Highlands, Mass., as-

signor to The Gamcwell Company, Newton,

Mass., a corporation of Massachusetts Application February 11, 1933, Serial No. 656,288 12 Claims. (01. 177-367) This invention relates to signaling systems and particularly to signaling systems utilizing code signal transmitters.

Such signaling systems ordinarily comprise a current source, manifesting apparatus, and a plurality of signal transmitting stations each having circuit breaking mechanism, and, in the instance of the usual fire alarm transmitters, electromagnetically controlled non-interference and succession mechanism connected in a normally closed metallic circuit.

In such systems, a break anywhere in the normally closed circuit renders all transmitting stations in such circuit ineffective for transmitting an intended signal to manifesting apparatus at a central office.

Various means have been suggested, heretofore, to make use of the ground as a common conductor from the current source at the central ofiice to the transmitting stations, 30 that, in the event the circuit is broken, a current path may be established from the current source over one side or the other of the broken circuit through central omce manifesting apparatus, the signal contacts and non-interference magnet in the transmitting station ar id then through the ground back to the current source. Such means have been objectionable for one reason or another, however, and have not been adopted for use with transmitters already in service, it being considered preferable to replace the transmitters by other mechanism adapted for the purpose, rather than to modify the existing transmitters to include such prior ground control means.

It is therefore an important object of this invention to provide simple and inexpensive means for automatically rendering the ground connection at a transmitting station effective for signaling over either side of a broken line, which means may be readily added to the great majority of transmitters now in common use.

In the meansheretofore employed for the control of a ground connection in a transmitter, additional contacts operated in various ways by the transmitter mechanism have been used. For reasons well understood by those skilled in this art such ground control contacts of any transmitter should be closed only during the transmission of a signal therefrom and may, therefore, remain unused for long periods of time. The force necessary to close such contacts so as to assure a positive, low resistance connection, following such long periods of disuse, is usually greater than that available for the transmitting mechanism.

It is, therefore, another object of this invention to provide means whereby the normally open ground connection at the transmitter is closed by a single contact arranged to be closed by movement of the manually operatedtransmitter start- 5 ing lever to starting position.

In some types of prior art transmitters having electromagnetic non-interference mechanism, the ground connections have been so applied that only one-half of the non-interference magnet winding has been effective when such transmitters were conditioned to utilize their ground connection for the transmission of their signals over one side or the other of a broken line. This is objectionable because the circuit resistance over one side of the line and through such grounds as are ordinarily available at signal boxes may be substantially greater than the normal metallic circuit resistance, and when only one-half of the magnet winding is effective during such circuit condition, energization of such magnet may be insufficient to assure complete effective transmission of thesignal.

Therefore, another object of this invention is' to so apply the ground connection at the transmitter that the entire winding of the non-interference magnet (which may also control succession mechanism) will at all times be in whatever current path is then effective for control by the signaling contacts.

Another object is to so apply a ground connection that the single pair of signaling contacts universally provided for signaling over the normally closed metallic circuit, will also be effective for signaling over one side or the other of a broken circuit.

A further object of the invention is the provision of a signal circuit having a transmitter therein and apparatus which, in the event a part of the normal signal circuit is faulty, as interrupted, automatically selects a sound part of the circuit for the transmission of its signal thereon.

Another object of the invention is the provision of a signaling system including a signal circuit and a transmitter therein and an asymmetric conductor so arranged that, when a part of the signal circuit is faulty or broken, the signal is caused to be directed through the unbroken portion of the signal circuit. a

A further object is generally to improve the construction and operation of signal circuits and signal transmitters.

Fig. 1 is a diagrammatic view of a signaling system embodying the present invention.

Fig. 2 is a diagrammatic view of the essential features of the circuit of Fig. 1 with much of the apparatus of Fig. 1 omitted.

As herein illustrated, the signaling system is adapted especially, although not restricted to the transmission of fire alarm signals and shows at B a fragmentary front elevation of a signaling train of a well-known and widely used form of fire alarm signal transmitting station or box, such, for example, as that shown by Patent No. 1,664,952 to Nathan H. Suren, with an illustrative embodiment of this invention applied thereto, together with diagrammatic representations of the circuit controlling means of two other; or more, similar stations at A and C, and central oflice signal responsive apparatus at M and M and a current source S.

The signaling train of station B may be briefly described as comprising a main wheel 2|, arranged for actuation by a spring 22 to drive the code wheel 23. A detent member, comprising the lever 26, is arranged to cooperate with the flange 21 carried by the wheel 2| in the usual manner, so that said mechanism is normally held at rest and so that momentary elevation of said lever will condition said train to permit a desired cycle of the operation thereof in the course of which said wheel 2| will so rotate as to cause a suitable number of revolutions of the code wheel 23, and hence rounds of the intended signal; following which said lever may move downwardly to its normal position and thereby cause the train to be again brought to rest, unless such movement of said lever is prevented by manipulation of the manually operable, so-called pull handle" 28, which is provided for facilitating actuation of the lever 26 to release the mechanism, or by other means such as will be presently described.

The signaling lever 29 is pivotally supported at 30, and carries the projection 3| for cooperation with the code wheel 23. The tall 32 is carried by and moves with said lever 29; the free end of said tail being arranged for cooperation with the pin 33 carried by the wheel 2| for holding said lever 29 away from said code wheel when the mechanism is at rest and also immediately after the starting thereof, until the first tooth or projection of said wheel has moved into the path of said projection 3|.

The lever 40 is pivoted at 4| and carries the armature 42 at the end thereof. The opposite end of said lever 40 carries a rearwardly extending projection 43 for cooperation with the pin 44 carried by the wheel 45 which rotates with the code wheel 23. As indicated by the dotted line 45a directly above the left hand edge of' the pin 44, said projection is so formed that, when the lever 40 is in the position which it occupies when the armature 42 is in fully attracted position, said pin may pass to the right of said projection and said projection extends to the left of said dotted line coextensively with the contour of the lever 40, as shown, so that when said lever-is in the position which it occupies when the armature 42 is in fully retracted position, said projection will be disposed within the are described by the revolution of said pin around the axis of the wheel 45 and will thus avoid engagement thereby, and so that when said lever occupies an intermediate position, to which it may be moved as is hereinafter more fully explained, said projection will be in the path of said pin for engagement thereby to move said lever to carry the armature 42 to its normal attracted position.

The pin 46 is carried by the lever 40 in such position as to be adapted for cooperation with the free end of the detent lever 26 as is hereinafter more fully explained, and the retractile spring 41 is suitably connected with said lever 40 and is of such strength as to prevent movement of said lever in response to the pull of the electromagnet when the armature 42 is in fully retracted position.

The signaling contacts 46 and 49 are arranged for actuation in the usual manner by the signaling lever 29; and the usual protective shunt contacts 5| and 52 are carried by the insulating blocks 53 and 54, respectively; said block 53 being fixed upon the frame plate 50 and said block 54 being so mounted upon the lever 26 that when said lever is positioned for restraining operation of the signaling train the contact 52 will engage the contact 5| and when said lever is positioned to permit operation of said train said contacts will be separated.

The faces 55 and 56 and the shoulder 51 are so formed in the free end of the lever 26 that, when said lever is positioned for restraining operation of the signaling train, said face 55 will so engage said pin 46 as to prevent movement of the lever 40 from attracted to retracted position; said face 56 is so positioned that movement of the detent lever 26 from its fully elevated position toward the position where it will cause the running of the signaling train to be arrested will cause said face to act through the pin 46 to move the lever 40 so as to bring the projection 43 carried thereby into the path of the pin 44; and the shoulder 51 is so positioned that. when the pin 46 is resting against the face 55, said shoulder will engage said pin during movement of the detent lever 26 away from its fully elevated position before such movement has proceeded to a point such as will cause the running of the signaling train to be arrested.

A pin 58 is carried by the armature lever 40 in such relationship to the extension 59 forming part of the signaling lever 29 that said signaling lever may assume the position which permits the contact 48 to move away from the contact 49 only while said armature is in its normal or attracted position, and such that said armature lever will be permitted to move to its abnormal or retracted position only while the contact 48 is in engagement with the contact 49.

The electromagnet Hill is cooperatively associated with the armature 42 for controlling noninterference and succession mechanism in a manner well understood by those skilled in this art and has one end of its winding connected through conductor I09 to the signaling contact 49, and the other end of its winding connected through conductor to the protective shunt contact 5|, and thence through conductor 18 to the main line terminal post H3. The other main line terminal post 2 is connected through conductor iii! to signaling contact 48 and also through conductor 8 to the protective shunt contact 52.

From the foregoing it will be seen that a signaling current path is provided from the post 2 through conductor I01 to signaling contact 48, thence through said contact and through contact 49, conductor I09, winding of magnet I00, conductors Ill and I08 to the other post H3; and that, when the detent lever 26 is normally positioned, a low resistance or shunt path is provided in parallel with said signaling path from said post 2, through conductor H6 protective shunt contacts 52 and 5|, and conductor I06 to post H3.

The signal transmitting apparatus thus far rangement as to assure a positive low resistance described is the signaling train of a well-known form of so-called perfect non-interference and succession" fire alarm box, and is here shown and described as typifying one of the forms of signal transmitting apparatus to which this invention may be applied, and it will be understood by those skilled in this art that this invention is suited for corresponding or similar application to other forms of signaling trains.

The three transmitting stations A, B, and C, are serially connected in a normally closed metallic circuit comprising conductors H6, H1, H9, and I 20, leading to the terminals T and T of the central office. A unidirectional current source, such as the battery S is provided at the central office. connected to the central office terminal T through conductor I2I, sign-a1 manifesting apparatus, such as the register M and conductor I22. The other terminal of the source S is connected to central office terminal T through conductor I23, signal manifesting apparatus, such as the register M and conductor I24. It should be understood that means for supplying a unidirectional current, such, for example, as an alternating current rectifier or a direct current generator, may be substituted for the battery indicated at S; and that other signal manifesting apparatus such, for example, as bells, lamps, etc., may be substituted for, or included in the circuit with, the registers M and M In accordance with this invention means are provided at each transmitter, operative in the event one side of the signal circuit is broken, for automatically causing the signal of the transmitter to be transmitted through ground and the unbroken side of the signal circuit. Said means includes asymmetric conducting media such as the rectifying unit R that is provided at each transmitting station and is connected to the main line terminal posts H2 and H3 thereat in such manner as to oppose current flow therethrough in the direction in which current is induced by the potential of the source S, being here shown as opposing current flow from post H3 to post H2. The asymmetric conductor or rectifying unit R may be of any well-known form such, for example, as the so-called dry disc type, and should have a center tap or connection intermediate the terminals thereof, as indicated at I 30. This connection divides the rectifier R into two serially connected sections l3l and I32 which are conductive in the same directions, the purpose of which will .be explained fully hereinafter.

It should be understood that while rectifying unit R may consist of any one of the more or less well known types of asymmetric conductive equipment-in any event, it should freely permit current flow therethrough in one direction and substantially exclude current flow in the other direction between the end or extreme terminals thereof, and its asymmetric conductive characteristic should be effective at both sides of its intermediate terminal or connection.

Each transmitter is provided with normally open ground contacts at I 35 and I36. Contact I36 is mounted on said insulating block 53 and contact I35 is so carried by said insulating block 53 that when the lever 26 is positioned to permit operation of the signaling train saidcontact I 35 will engage contact I36. It should be noted that the ground contacts I35 and I 36 are closed by the manual operation of the transmitter pull handle 28 and are of such proportions and ar- One terminal of such source is connection when closed. The contacts are so arranged and located that they can be applied readily to existing transmitters for operation in accordance with this invention. 7

The center tap or connection I 30 of the asymmetric conductor or rectifier R is connected through conductor I33 to ground contact I 35, and the other ground contact is connected through conductor I31 to the terminal I38 which terminal is connected to the ground or other suitable common return conductor.

The central office current source S also has a center tap or connection I25 electrically inter-' mediate to the terminals thereof which connection is permanently connected to the ground or other common return conductor.

If the resistance of the metallic circuit outside of the central oflice terminals T and 'I is low in comparison to the resistance of the manifesting apparatus at M and M, as would frequently be the case in actual practice, there will .be little if any current flow through the ground or common return conductor G because of a ground connection at any transmitting station while the outside line is closed. Hence, no' responsive apparatus is deemed necessary in the ground lead from the center connection I25 of the current source S, inasmuch as the apparatus at M and M2, as will be more fully explained hereinafter,-

will respond to signals from any station connected in the outside line under all circuit conditions except from stations located between two breaks, two ground connections, or between a ground con nection and a break in the outside metallic circuit, or from stations shunted by a short-circuit around the terminals thereof, such, for example, as might be caused by a connection between the wires leading to such stations.

The operation of a transmitting station such as station B, while the circuit is normally conditioned, is substantially the same as that of a well-known type of perfect non-interference and succession fire alarm signaling box, which is well understood by those skilled in this art, and will therefore not be here described in detail. It

should, however, be noted that, throughout activity of station B, the normally open ground lishing a current path from the center connection I30 of the asymmetric conductor or rectifier R to the ground terminal I38. Although this ground current path does not affect operation of the transmitter B or response thereto of manifesting apparatus M or M under normal circuit conditions, it is effective during abnormal circuit conditions as will be described hereinafter.

In the event that the normal all metallic current path is broken, as by rupture of conductor H6 or III, and the transmitting mechanism at station E is started by actuation of pull handle 28,-the operation is as follows:

Detent lever 26 will be elevated, thereby moving contact 52 away from contact 5i so as to break the protective shunt around the winding of magnet I 06 and the signaling contacts 49 and 48 as well as around the rectifier R. Such movement of the lever 26 by the pull handle 28 will also raise contact I35 into engagement with contact I36, thereby closing the normally open current path from the connection I30 of rectifier R to the ground terminal I36.

Closing of ground contacts I35 and I36 completes an emergency current path from the positive terminal of source S through conductor I23,

register M, conductor I20, to terminal T, through conductor I20, station C and conductor to post II3 of station B, thence through conductors I 00 and III, winding of magnet I00, conductor I03, signaling contacts 40 and I8, and conductor I0I to post II2, thence through section I 3I of rectifying unit R to the center connection I30 thereof, thence through conductor I33, ground contacts I35 and I30 and conductor I31 to the ground terminal I38, and thence through the ground or other common conductor to the center connection I25 of source S.

From the foregoing it will be seen that the current path established by the closing of contacts I35 and I30 serially includes one-half of the current source S, the manfcsting device M and the entire winding of magnet I00 and the signaling contacts of station B.

The transmitting mechanism 'of station B thereupon proceeds to transmit its signal by the breaking and making of this emergency current path, in the same manner as when signaling over a normally ciosed all metallic circuit, which may be summarized as follows:

When the detent lever 28 has been sufficiently raised, the signaling train will start running, and thereby rotate the code wheel 23. Such rotation of the code wheel 23 will bring the first of the code teeth carried thereby into the path of the projection 3| of the signaling lever 29 and, thereupon, the pin 33 will be withdrawn from the path of the tail 32 of said signaling lever, so as no longer to prevent said lever from following the outline of said code wheel. If the electromagnet I00 remains energized until the first tooth of the code wheel 23 is withdrawn from the path of theprojection 3i, the signaling lever 29 will be moved downwardly in response to the tension of the contact l0, and said contact will thereupon move away from the contact 49; thereby interrupting the current path through the signal responsive apparatus at M and magnet I00. Upon such circuit interruption, said responsive apparatus M will act in response thereto, but the armature 02 will not be permitted to move away from the magnet I00 because the downward movement of the signaling lever 29, incident to the circuit interruption, carried the extension 50 thereof into the path of the pin 58 and thereby held the lever 00 from movement in response to the retractile spring 41 upon de-energi tion of the magnet I00. It will be understoo that the circuit will be alternately closed and broken in accordance with the outline of the code wheel 23 so as to correspondingly cause the manifestation of the intended code signal by the responsive apparatus at M.

After a predetermined cycle of the operation of such train (usually four so-called rounds or revolutions of the code wheel 23) the detent lever 26 will return to its normal position and thereby carry the ground contact I35 down out of engagement with its cooperating contact I36 and thus restore the ground connection to its normal open circuit condition.

The train will be brought to rest thereafter as soon as the wheel 2| has reached the position which causes the pin 33 to engage the tall 32 of the signaling lever 29 and thereby cause said lever to move the signaling contact 08 to its normal position.

In the event that the normal all metallic" current path is broken on the other side of station B, as by rupture oi conductor H9 or I20, and the transmitter mechanism at station B is then started by actuation of pull handle 28, the operation is as follows:

The shunt contacts BI and 52 will be opened and the ground contacts I35 and I38 will close the normally open current path from the connection I30 of rectifier R to the ground terminal I33 in response to pulling of handle 28, as hereinbefore more fully explained.

Closing of ground contacts I35 and I36 com pletes an emergency current path from the center connection I25 of the current source S through the ground or other common conductor G, ground terminal I38 of station B, conductor I31, ground contacts I36 and I35, conductor I33 to the center connection of the asymmetric conductor or rectiiler unit R, thence through section I32 of said unit to main line terminal post II3, thence through conductors I08 and III, winding of magnet I00, conductor I09, signaling contacts 48 and 48, conductor I01, post II2, conductor III, station A, conductor IIG, terminal T conductor I2I,' register M and conductor I22 to the negative terminal of the source S.

From the foregoing it will be seen that the current, path thus established serially includes onehalf of the current source S, the entire winding of magnet I00 and the signaling contacts of station B, and manifesting device M The mechanism of station B thereupon proceeds to transmit its signal by the breaking and making of this emergency current path, in the same manner as just described in detail in connection with a break in the other side of the line, except that such signal will be responded to by the responsive apparatus at M instead of by the apparatus at M In the event that the transmitting mechanism at two stations, such, for example, as stations A and B, are started simultaneously at a time when the metallic circuit is otherwise normally conditioned, the gzound paths at such stations will be closed, thereby completing independent current paths from the active stations over the respective sides of the line whereby the complete signal from station A will be responded to by the apparatus at M and the complete signal from station B will be responded to by the apparatus at M, in the following manner:

Closing of the ground contacts I35 and I36 at station B establishes an emergency signaling path over the right hand side of the line corresponding to that described in detail in connection with operation when conductor H6 or II! is broken. It will therefore be obvious that breaking of the left hand side of the metallic circult by activity of the signaling contacts of station A cannot affect the response of apparatus at M to the signals from station B.

Correspondlngly, closing of the ground contacts I35 and I36 -at station A establishes an emergency signaling path over the left hand side of the line similar to that described in detail in connection with operation when conductor H0 or I20 is broken, and it will therefore be obvious that activity of station B cannot interfere with the response of apparatus at M to the signals from station A.

Although the complete signals from two such simultaneously active stations will be completely responded to by the respective devices M and M should the mechanism at one of such stations complete its signal and open its ground path before the mechanism at the other station has completed its signal, the remaining portion of such signal will be responded to by both regisnaling paths established by the stations, such ters M and M. For example, if the signal transmitted from station A is I2I and the signal from station B is 32 I, and the mechanism at both stations each transmit four complete rounds of their respective signals, the timing of the transmitting mechanism may be such that station A will complete its transmission of four complete rounds of signal I2I and open its ground path during the transmission of the last round of signal 32I from station B. The register or other responsive apparatus at M will then respond to the remaining fragment of the signal from station B.

In the event that the transmitting mechanism at station A is started at a time when the metallic circuit is in normal condition and, after the apparatus at M and M has responded to a portion of such signal, the transmitting mechanism at station B is started, the response of apparatus at M to the signal from station A will be terminated and such apparatus will thereafter respond only to the signal from station B until the complete four rounds of such signal has been transmitted; following which, the apparatus at M will again respond to the signal from station A, if transmission of same has not been completed. For example, assuming that the signal from station A is 532 and the signal from station B is 2|, and that each mechanism is arranged to transmit its signal four complete rounds, and further assuming that station A is started first and, after transmitting a portion of the first round of its signal, for example, 53 the transmitting mechanism station B is then started-the timing of the two transmitting mechanisms might be such that the record on the tape of a register at M would show the number 53, then four rounds or repetitions of the signal 2i from station B, and then a fragment such as 22 of the later part of the third round of signal 532 from station A, followed by the numher 532 representing the fourth complete round from station A. During such' activity of these two stations, the tape of a register at M would show only the four complete rounds of the signal 532 from station A.

If the numbers transmittedby the two stations A and B were nearer the same length, such, for example, as 32! and 324,-and the mechanism at station B is started after station A has transmitted, say one round; a register at M will first record the complete four rounds of signal 32! from station A and then the remaining portion of the signal from station B, and a register at M will first record that portion of the signal transmitted from station A before the mechanism at station B was started and then record the four complete rounds of signal 324 from station B.

In the event that, during concurrent activity of two stations, such, for example, as stations A and B as just described, the mechanism at a third station, as at station C, is started-the closing of the ground path at such third station in response to the starting thereof will render intervening stations, such as station B, inefiective for causing, response of apparatus at either M or M The signal from station C will thereupon be responded to by the apparatus at M and the apparatus at M will continue to respond to the signal from station A. I

The reason that intervening stations, such as station B, are rendered ineffective for causing response of apparatusat M or M is that such stations are not included in the emergency sigmovement of lever as A and C, which are located in the circuit nearer to the central ofiice terminals. Inasmuch as magnet I00 of station B is thus excluded from effective current paths, such magnet will not be energized. Armature 42 thereof will therefore fall away to fully retracted position and the non-- interference and succession mechanism will function in the usual manner, which may be briefly described as follows:

Such retraction of armature 42 carries pin 58 into the path of extension 59 of the signaling lever 29 and thereby prevents movement of the signaling lever from circuit closing position. When the armature 42 of station B has moved to its retracted position, as just described, it will remain in such position until the end of a predetermined cycle of operation of the signaling train, whereupon the projection 62 carried by lever 26 enters notch BI in flange 21 and said lever 26 will move away from its fully elevated position. Suchmovement of this lever, at a time when the armature is in retracted position, is arrested by engagement of the shoulder 51 formed in the end thereof with the pin 46 carried by the armature lever 40.

26 is not sufiicient to permit opening of the ground contacts I35 and I36 or to cause the running of the signaling train to be arrested, but is such that engagement of the face 56 thereof with pin 46 will move lever 40 to a position where the projection 4.3 will be in the path of the pin 44.

Succeeding rotation of wheel 45 incident to running of the signaling train will cause the armature 42 to be moved approximately to its fully attracted position by the engagement of the projection 43 by the pin 44 and, if the mechanism at either station A or station C has completed transmission of its signal and opened its ground connection, armature 42 of station B will beheld in its fully attracted position by energization of its magnet I00 and this mechanism will then again be eiTective for transmitting its signal to the responsive apparatus at either M or M or both, depending upon which, if either, of station A or station C is still active. If station A is still active, the signal from station B will be responded to by the apparatus at M only, until such time as station A completes its activity and removes its ground connection, whereupon the remainder of the signal from station B will be responded to by the apparatus at both M and M correspondingly, if station C is still active, the signal from station B will be responded to by the apparatus at M only, until completion of the signal from station C and the removal of its ground connection, whereupon the remainder of the signal from station B will be responded to by the apparatus at both M and M If at a time when the metallic circuit is open between station B and the positive terminal of source S, the transmitting mechanism at station A is first started and the then mechanism at station B is started, the complete signal of station A will be responded to by the apparatus at M and the non-interference and succession mechanism of station B will delay transmission of the signal from this station until station A has completed its signal and removed its ground connection. Station B will then proceed with the transmission of the complete four rounds of its signal, provided, of course, that the capacity of its main spring 22 has not been exhausted.

This limited Such signal will also be responded to by the apparatus at M.

If, however, under the conditions just referred to, the transmitting mechanism at station B is first started and then the mechanism at station A is started, the apparatus at M will first respond to that portion of the signal from station B which is transmitted before the mechanism at station A is started, and then will respond to the complete signal from station A. The starting of the transmitting mechanism at station A will prevent energization of the magnet I00 of station B from the source S and the non-interference and succession mechanism thereat will then act to delay transmission of its signal until station A has completed its signal and removed its ground connection. Station B will then again proceed with the transmission of its signal, provided, of course, that the capacity of its spring 22 has not been exhausted, and the apparatus at M will then respond to this signal also.

It will thus be seen that, under the condition just described, the tape of a register at M would record a fragment of the signal from station B, then the complete signal from station A, and then would respond to the complete four rounds of the signal from station B.

From the foregoing it will be apparent that any number of stations may be started simultaneously or one after another on an otherwise normal metallic circuit and the apparatus at M and W will at all times respond to the two of such active stations which are nearest to the respective terminals of source S. The complete signals from all such active stations, in addition to possible fragments of some or all of such signals, will therefore be responded to, either by the apparatus at M or the apparatus at M, provided that the driving power for such stations does not become exhausted.

It will also be apparent that any number of stations may be started on one side or the other or on both sides of a break in the metallic circuit, and the complete signals from all such stations (in addition to possible fragments of some or all of such signals) will be responded to, either by the apparatus at M or the apparatus at M. The apparatus at M will respond to the signals from all stations to the left of the break and the apparatus at M will respond to the signals from all stations to the right of the break.

Although a non-interference and succession type of signaling mechanism has been selected for the purpose of illustrating this invention, such non-interference and succession mechanism is not essential to practicing of certain aspects of this invention.

Without such mechanism, the response of apparatus such as M and M to signals from stations under various conditions will be as hereinbefore fully described in connection with signaling apparatus such as illustrated at A, B, and C, except in cases where the signal from a given station is cut off from the control of the responsive apparatus, as by the concurrent ac tivity of stations on respective sides thereof, or by a break in the metallic circuit on one side and an active station on the other side thereof. In such a case, the transmitting mechanism of the ,cut oil station will continue to run and, after stations, one thereof between such cut 03 mechanism and the central oiilce completes its signal and removes its ground connection before such mechanism has completed formulation of its signal, the remaining portion of such signal will 5 then be responded to by appropriate one of the responsive devices at the central omce.

It should be understood that the formof mechanism indicated by the accompanying drawing and hereinbefore described in detail, is selected 10 for the purpose of illustrating this invention because it is familiar to those skilled in this art, and is susceptible of ready illustration and description. It is believed that, in view of the foregoing detailed description, the application 15 of this invention to other prior art signaling mechanisms will be apparent to those skilled in this art.

I claim: r

1. A signaling system comprising a signal cir- 20 cuit having a unidirectional current source therein, a signal transmitter in said circuit having normally closed contacts for formulating code signals, an asymmetric conductor in parallel with said contacts and opposed to the potential 25 of said circuit, and means controlled by said transmitter for establishing connection between an intermediate part of said asymmetric conductor and an intermediate part of said current source.

2. A signal transmitter having actuating mechanism, signaling contacts operated thereby, an asymmetric conductor having serially connected sections connectedin parallel with said contacts in opposition to the potential thereof, and 35 grounding contacts operated by said mechanism for grounding said asymmetric conductor between sections thereof.

3. A signaling system comprising a signal circuit having a unidirectional current source therein provided with a grounded intermediate connection, manifesting apparatus in said circuit on both sides of said current source, a signal transmitter in said circuit having normally closed contacts for formulating sode signals, an asymmetric conductor in parallel with said contacts and opposed to the potential of said current source, and grounding contacts controlled by said transmitter for grounding an intermediate part of said asymmetric conductor.

4. A signal transmitter having two normal line terminals and a third auxiliary terminal, a single pair of signal contacts, and means involving respective portions of an asymmetric conductor for providing connections between said auxiliary terminal and one and the other of said normal terminals of such character that said signal contacts are included both in the path effective for current flow in a predetermined direction between said auxiliary terminal and 60 a certain one of said line terminals and in the path efiective for current flow in a predetermined direction between said auxiliary terminal and the other of said line terminals.

5. A signal transmitter having two line terminals and a ground terminal, a normally closed metallic circuit current path between said line terminals, and a signaling contact operable to interrupt said path, in combination with asymmetric conducting media having terminals connected between said line terminals, and means for rendering said media effective for permitting signal transmitting current flow between said ground terminal and a point intermediate the terminals of said. media.

6. A signaling system comprising a signal transmitter having a single pair of signal transmitting contacts, a non-interference winding in series with said contacts, a circuit including a Unidirectional current source over which the signals of said transmitter are normally trans mitted, and an emergency conductor connected with an intermediate part of said current source, said transmitter having means including an asymmetric conductor connected in shunt relationship to said contacts and winding and in such polarity as to be operative in the event of a break in 'a portion of said circuit for selecting for signal transmission from said transmitter the unbroken part of said circuit and said emergency conductor.

7. A signal transmitter having actuating mechanism and three terminals, a normally closed metallic circuit current path between two of said terminals, succession mechanism comprising an electromagnet serially included in said path and a circuit controller governed by said magnet having means for breaking said normally closed path, in combination with an asymmetric conductor connected between said two terminals, and means operable by said actuating mecha nism for establishing a. current path from a point intermediate the terminals of said conductor and the third one of said three terminals, said conductor being asymmetric in the same direction on both sides of said intermediate point.

8. A signal transmitter having actuating mechanism and a member for controlling the operation thereof, three terminals, a normally closed metallic circuit current path between two of said a signaling contact thereby to interrupt said path, in combetween said two terminals, and means operable by said actuating mechanism for establishing'a current path'from a point intermediate the tersaid terminals when said member is conditioned to permit operation of said transmitting apparatus, said conductor being asymmetric in the same direction on both sides of saidintermediate point. I

9. A signal transmitter having actuating mechanism and three terminals, a normally closed metallic circuit current path between two of said .terrupt said path,

terminals, and a signaling contact operable to inin combination with an asymmetric conductor connected between said two terminals, and means operable by said actuating mechanism for establishing a current path from a point intermediate the terminals of said conductor and the third one of said terminals, said conductor being asymmetric in the same direction on both sides of said intermediate point.

10. A signal transmitter having actuating mechanism, signaling contacts operated thereby, a succession magnet winding in series with said contacts, an asymmetric conductor in parallel with said contacts and winding, said asymmetric arranged to oppose intended current-flow therethrough between its terminals, and grounding contacts controlled by said mechanism for grounding an intermediate part of said asymmetric conductor, said conductor being asymmetric in the same direction on both sides 01' said intermediate part.

11. A signaling system comprising a. signal circuit having a unidirectional current source therein provided with a grounded intermediate connection, a plurality of signal transmitters arranged in series in said circuit and each having a succession magnet winding and normally closed contacts for formulating code signals in said circuit, an asymmetric conductor in parallel with the winding and contacts of each signal transmitter, a separate ground connection for an intermediate part of each conductor, and contacts controlled by respective ones of said transmitters for controlling their associated ground connections, each said conductor being asymmetric in the same direction on both sides 01' said intermediate part.

12. A signal transmitter having actuating mechanism, signaling contacts operated thereby, an asymmetric .conductor having serially connected sections connected in parallel with said contacts in opposition to the potential thereof, two

line terminals and a ground terminal, connections for seriallyassociating said signalling contacts between two of said terminals and for connecting the third 01' said terminals to said asymmetric conductor between sections thereof, and a contact operated by said mechanism for governing the eflfectiveness of the connection with said ground terminal;

FOSTER E. WELD. 

